You may be asking, what ARE climate-smart soils?
Climate-Smart Soils: A concept
The concept of climate-smart soils originated in the 2016 Nature paper by Paustian et al. The key is that soils have the capacity to sequester carbon and remove it from the atmosphere, thus helping the fight against climate change!
This depends on management, however. Soils also release greenhouse gases, especially agricultural soils which contribute a major share (37%) of agricultural emissions, mainly from carbon dioxide (CO2) and nitrous oxide (N2O, which comes mostly from nitrogen fertilizer applied to the soil). Improved soil management can reduce these emissions by converting the CO2 taken up by plants into soil organic matter.
A pathway to implementation
Paustian et al. suggest a path from research and monitoring > practices to sequester carbon in the soil and reduce agricultural greenhouse gas emissions > policies and systems to support implementation. Our program aims to expose our scholars to all these steps, so that they can work at implementing real solutions!
Climate-Smart Soil Practices: Carbon Sequestration
Our team has been hard at work researching and monitoring different agricultural systems to determine practices that are ‘climate-smart’. While this is always a work in progress (and something our scholars will be working hard on!), some of the results of our research show that climate-smart soils can have increased carbon sequestration through:
- Crop rotation: this paper from CREATE-CSS investigator Kate Congreves illustrates that rotations including crops with higher residue & carbon inputs had higher soil organic carbon!
- Note: CREATE-CSS investigator Myrna Simpson showed that plant chemistry impacts soil organic carbon as well; the kind of plant that you grow (or which part you leave in the field) matters!
- ‘Perennializing’ systems (converting to year-round crops): this provides year-round carbon inputs, like this paper from CREATE-CSS investigators Mario Tenuta & Martin Entz (they also found improved rotation + organic management = increased microbial biomass carbon!)
- Organic amendments: amendments such as manure, compost, or other bio-waste products add carbon to the soil, which can be stabilized as soil organic carbon, as shown by CREATE-CSS investigator David Burton.
- Reduced or no-till: adopting no-till and including winter wheat rotations are key to improving soil health attributes like aggregate stability and storage of C and N, shown in Ontario in this paper with CREATE-CSS co-investigator Kate Congreves in 2014.
- Maintaining native systems: Increasing yields on productive lands to avoid conversion and degradation of native ecosystems (with typically higher carbon stores) in the first place; this paper from the UK talks about the concept of ‘land sparing’ to offset greenhouse gas. emissions
- An added (but important!) note: soil microbes are VERY important to soil carbon capture; many of our CREATE-CSS investigators including Myrna Simpson, Kari Dunfield and Cynthia Kallenbach research how soil microbes participate in the carbon cycle. See this paper by Kallenbach.
Climate-Smart Soil Practices: Greenhouse Gas Emission Reduction
Climate-smart soils also work to decrease the release of other greenhouse gases; nitrous oxide (N2O) and sometimes methane (CH4):
- Nitrification inhibitors: these enhanced-efficiency fertilizers delay the conversion of fertilizer nitrogen into nitrate (NO3), and thus N2O, until the plant needs it (reducing emissions!), which was found by CREATE-CSS investigator Mario Tenuta in this 2014 paper.
- Correct placement and timing of fertilizers: as a part of the 4R Nutrient Stewardship program (Right Source @ Right Rate, Right Time, Right Place), lead CREATE-CSS investigator Claudia Wagner-Riddle found that applying nitrogen as a side-dress when the corn needed the most nitrogen reduced N2O emissions!
- Reduced tillage: CREATE-CSS investigators (and female researcher powerhouses!) Claudia Wagner-Riddle, Kate Congreves and Kari Dunfield found higher N2O emissions in tilled fields over the winter (residue removal also increased N2O emissions – so leave residues in the field!)
- Conversely (and just to show that science is never easy), CREATE-CSS investigator David Burton found increased N2O emissions during the growing season in no-tilled fields over conventional fields;
- What does this mean? It means that more research is required to understand which conditions lead to N2O release, and also that practices that are beneficial in one way – increasing soil carbon! – may have trade-offs somewhere else. Thus we need to look at the whole system in order to make management recommendations!
Challenges to Implementation
Paustian et al. identify challenges in determining global potential for soil greenhouse gas mitigation. A significant challenge is to distinguish between what is technically feasible to sequester carbon or reduce greenhouse gas emissions, and what we can practically achieve given economic, social and policy constraints. This is a huge problem in agricultural research, which often focuses on the ‘technically feasible’.
This is why our scholars will learn about real farmers and their real challenges, as well as mechanisms to incentivize carbon-sequestering practices!
As Paustian says, “Climate change and greenhouse gas mitigation require an ‘all of the above’ approach, where all reduction measures that are feasible, cost-effective and environmentally sustainable should be pursued.”